#box{
    position: absolute;
    top: 50%;
    left: 50%;
    margin:-100px 0 0 -100px;
    width: 200px;
    height: 200px;
    background-color: #f00;
    font-size: 14px;
    text-align: center;
    line-height: 200px;
    color: #fff;
}